There are 2 ways to attempt to unlock the door to access the sensor:

Occasionally,you can turn the power off to the oven for a few seconds(10 to 20) when you re establish power the door latch motor may run,and if you catch it in the unlock position you can open the door, then it will go back to the F3 code.

If that does not work, you'll have to manually un lock the door,

You'll need a coat hanger or other semi flexible article (approx. 6" long).

You need to insert the coat hanger (hook end to the right)between the door and oven front frame(hook needs to be off center of the door 1 or2").

Pull the hanger to left, until the hook catches the latch, push in on the door slightly(relieves pressure on the latch) and pull the hanger another 1/4 to 1/2" and open door.

I always used a coat hanger,(had it configured just for this purpose) if you use something else you may have to insert it from the top of the door,in the same manner as the hanger and push to the left.

It may take a few tries, but you'll get it ... Then change the sensor.

;) :)